This is a continuation-in-part of copending application Ser. No. 338,978 entitled Ultrafine Sheath-Core Composite Fibers and Composite Sheets Made Thereof, which was filed on Jan. 12, 1982, by the same applicants.
Ultrafine fibers and artificial leathers prepared by using ultrafine fibers are known. In the case of artificial leathers made of ultrafine polyamide fibers, such as nylon 6 raised fibers are readily entangled and a beautiful appearance can not easily be obtained. Polyacrylonitrile ultrafine fibers are dissolved in a polyurethane (referred to PU hereinafter) solvent or deteriorated therein. In general, polyester ultrafine fibers such as polyethylene terephthalate (referred to PET hereinafter) ultrafine fibers give a harder or stiffer suede-like artificial leather because of the relation between the PU binder and the fibers than an artificial leather made of nylon 6 or nylon 66 ultrafine fibers. Moreover artificial leathers made of polyester ultrafine fibers such as PET are defective in that the fibers cannot be dyed with a cationic dye and a brilliant dyed color cannot be obtained and that the raised fibers are not soft enough. Moreover, the polyester ultrafine fibers can not easily be dyed a deep color with disperse dye while maintaining color fastness and hence, the dyeing cost is increased.
Moreover, in general, one must use a much greater amount of disperse dye than cationic dye.
A cationic dyeable polyester ultrafine fiber is very weak in strength and does not give strong artificial suede. A cationic dyeable polyester which is copolymerized sufficiently to be dyed a deep color does not have enough fiber strength even if the degree of polymerization is increased to the limit of spinnability.